The knee joint basically consists of the bone interface of the distal end of the femur and the proximal end of the tibia. Appearing to cover or at least partially protect this interface is the patella, which is a sesamoid bone within the tendon of the long muscle (quadriceps) on the front of the thigh. This tendon inserts into the tibial tuberosity and the posterior surface of the patella is smooth and glides over the femur.
The femur is configured with two knob like processes (the medial condyle and the lateral condyle) which are substantially smooth and which articulate with the medial plateau and the lateral plateau of the tibia, respectively. The plateaus of the tibia are substantially smooth and slightly cupped thereby providing a slight receptacle for receipt of the femoral condyles.
When the knee joint is damaged whether as a result of an accident or illness, a prosthetic replacement of the damaged joint may be necessary to relieve pain and to restore normal use to the joint. Typically the entire knee joint is replaced by means of a surgical procedure that involves removal of the surfaces of the corresponding damaged bones and replacement of these surfaces with prosthetic implants. This replacement of a native knee joint with a prosthetic joint is referred to as a primary total-knee arthroplasty.
On occasion, the primary knee prostheses fails. Failure can result from many causes, including wear, aseptic loosening, osteolysis, ligamentous instability, arthrofibrosis and patellofemoral complications. When the failure is debilitating, revision knee surgery may be necessary. In a revision, the primary knee prosthesis is removed and replaced with components of a revision prosthetic knee system.
Knee implant systems for both primary and revision applications are available from a variety of manufacturers, including DePuy Orthopaedics, Inc. of Warsaw, Ind. DePuy and others offer several different systems for both primary and revision applications. For example, DePuy Orthopaedics offers the P.F.C. SIGMA® Knee System, the LCS® Total Knee System, and the S-ROM Modular Total Knee System. Each of these orthopaedic knee systems includes several components, some appropriate for use in primary knee arthroplasty and some appropriate for use in revision surgery.
DePuy Orthopaedics also offers other orthopaedic implant systems for other applications. One such system is the LPS System. The LPS System is provided for use in cases of severe trauma and disease. In such cases, the trauma or disease can lead to significant amounts of bone loss. The LPS System provides components that can replace all or significant portions of a particular bone, such as the femur. The DePuy LPS System is described more fully in U.S. patent application Ser. No. 10/135,791, entitled “Modular Limb Preservation System”, filed Apr. 30, 2002 by Hazebrouck et al., which is incorporated by reference herein in its entirety.
In some patients, the metaphysis of the bone near the joint presents cavitary defects that are not completely filled by standard knee implants. The presence of such metaphyseal defects can result in loosening of the prosthetic implant over time, compromising the stability of the prosthetic implant and frequently requiring revision of the prosthetic implant.
To fill metaphyseal cavitary defects, knee systems with modular metaphyseal sleeves have been provided. Such sleeves are illustrated, for example, in: U.S. Pat. Pub. No. 2010/0114323, entitled “Knee Prosthesis Kit with Winged Sleeves and Milling Guide;” U.S. Pat. Pub. No. 2006/0030945A1, entitled “Modular Orthopaedic Implant System With Multi-Use Stems;” U.S. Pat. No. 7,799,085, entitled “Modular Implant System With Fully Porous Coated Sleeve;” U.S. Pat. No. 7,291,174, entitled “Prosthetic Tibial Component With Modular Sleeve;” U.S. Pat. No. 6,171,342, entitled “Medical Fastening System;” U.S. Pat. No. 5,824,097, entitled “Medical Fastening System;” U.S. Pat. No. 5,782,921, entitled “Modular Knee Prosthesis;” and U.S. Pat. No. 4,634,444, entitled “Semi-Constrained Artificial Joint.” Such sleeves have been used in commercially available prosthetic knee implant systems, such as the P.F.C. SIGMA.® Knee System, the LCS® Total Knee System, the S-ROM Modular Total Knee System and the LPS System, all available from DePuy Orthopaedics, Inc. of Warsaw, Ind.
Modular sleeves have also been used in hip implant systems, as illustrated, for example, in: U.S. Pat. No. 6,264,699, entitled “Modular Stem and Sleeve Prosthesis;” and U.S. Pat. No. 4,790,852, entitled “Sleeves for Affixing Artificial Joints to Bone.” Such hip sleeves have been used in commercially available prosthetic hip implant systems, such as the S-ROM hip systems, available from DePuy Orthopaedics, Inc. of Warsaw, Ind.
The disclosures of all of the above patent applications and patents are incorporated by reference herein in their entireties.
In knee systems with modular metaphyseal sleeves, the conventional shape of many of the sleeves is generally an elliptical cone with a large ellipse profile close to the joint line tapering down to a smaller elliptical or circular profile at the termination of the component distal to the joint line. Generally, the sleeves have a terraced or stepped outer surface and an inner channel for frictional fixation to another component. This geometry fills cavitary defects in the metaphysis, allows for a wider surface area for load transfer through the joint and provides rotational stability for the articulating components of the prosthesis.
In some knee-arthroplasty patients, metaphyseal defects may be single sided: there may be a medial or lateral defect that requires use of a metaphyseal sleeve but the opposite side may have healthier bone. To use a conventional symmetric sleeve in such cases would require the sacrifice of some healthy bone that could have been left in place to provide support for the prosthesis. Some have attempted to address single-side defects through use of augments; however, such systems address only peripheral defects and do not account for situations where the peripheral bone is intact but there is a central void.
U.S. Pat. Pub. No. 2010/0114323, entitled “Knee Prosthesis Kit with Winged Sleeves and Milling Guide,” referenced above, discloses an asymmetric metaphyseal sleeve that may be advantageously used in patients having single-side defects in the metaphysis. The metaphyseal sleeves illustrated in that patent application include two forms, one with a single protrusion (wing or spout) to extend in a generally medial or lateral direction in the case of a non-centralized defect in the tibia or femur and one with two protrusions (wings or spouts) to extend in both a generally medial or lateral direction in the case of a centralized defect in the tibia or femur.
In hip systems with modular metaphyseal sleeves, the conventional shape of many of the sleeves is generally a frusto-conical cone with a protrusion (wing or spout) extending radially outward. The spout or wing is intended to be placed on the medial side of the proximal hip metaphysis, opposite from the greater trochanter. Generally, such hip sleeves also have a terraced or stepped outer surface and an inner channel for frictional fixation to another component. This geometry fills cavitary defects in the medial metaphysis, allows for a wider surface area for load transfer through the joint and provides rotational stability for the articulating components of the prosthesis.